Prospects of high-energy nuclear physics • Status and prospects – LHC, FAIR, NICA •ALICE – Great Russian & JINR Contribution – Great success! Detectors work very well, results are coming – Look forward at first HI data, discovery machine from day one • FUTURE – Fertile field for science and for Italian-Russian Collaboration • ALICE various detectors (direct collaboration in the muons arm, Particle ID (TOF and HMPID), ITS, and collaboration on Physics analysis • Important to complete the program and the detector (PHOS) Paolo Giubellino • A relevant program of Upgrades already developing = > INFN Torino room for important collaboration ITALY-RUSSIA • NICA is an opportunity to be explored Round Table December 19 2009 A bit of history: / 2007 Accelerators 2008 2009 of Heavy Ions 2010 • Experimental programs with High Energy nuclear beams have been carried out for more >1986 than 20 years • After the pioneering work at the Bevalac in the late seventies, 4 facilities at really high energy: AGS, SPS, RHIC and LHC • Two communities joined: • particle physicists • nuclear physicists
•Latest news: Pb injection in the LHC performed succesfully! H. Specht, 1992 Very difficult experiments...
central Au-Au event @ ~130 GeV/nucleon CM energy
STAR … a developing field! • SPIRES query for all publications with QGP, SQGP, QUARK-GLUON PLASMA, QCD PLASMA, STRONGLY COUPLED PLASMA, STRONGLY-COUPLED PLASMA in their title:
Field has gone from the periphery into a central activity of contemporary Nuclear Physics Nuclear Physics has changed a lot…
Eiffel tower ALICE • Size, ~ 7300 tons magnet complexity and ~ 8000 tons time span of projects have grown enormously, and they develop over decades, carried by large international collaborations Even the “simplest” element requiresAluminum te know- from Armenia how and contribution from all over the world Steel cone from Finland Example: the ALICE Muon Absorber – complex mechanical piece ~ 100 tons ~ 18 m Concrete from France, Engineering & Supervision by CERN Design• by optimized Russia (Sarov/ISTC) material content Graphite & Steel from India W, Pb, Fe, graphite, Boron, plastic, concrete,.. • carefully chosen Leadgeometry from England – minimize cost via design by factor 2!
• and by worldwide Italian polyethylene Support from Italy bargain hunting Tungsten from China To do what? … explained very well by Prof. Di Giacomo just now! Early Ideas • Hagedorn 1965: mass spectrum of hadronic states
=> Critical temprature Tc=B • QCD 1973: asymptotic freedom Quantum Chromo Dynamics (QCD) is the theory that describes the interactions between – D.J.Gross and F.Wilczek, H.D. Politzer quarks and gluons [Nobel Prize 2004] • 1975: asymptotic QCD and deconfined quarks and gluons – N. Cabibbo and G. Parisi, J. Collins and M. Perry Interpretation of the Hagedorn temperature as a phase transition rather than a limitingT: “We suggest … a different phase of the vacuum in which quarks are not confined” First schematic phase diagram (Cabibbo and Parisi, 1975) Exploring the QCD phase diagram T.D. Lee (1975) “it would be interesting to explore new phenomena by distributing a high amount of energy or high nuclear density over a relatively large volume “ How? Colliding nuclei at very high energy Complex picture, with many features
quark-gluon plasma (QGP) Tc Early universe χ−symmetric
hadron gas χ− Symmetry Broken
Temperature Colour super nucleon gas nuclei conductor neutron stars net baryon density ρ0 Phase diagram for H O 2 Critical endpoint Study how collective phenomena and macroscopic properties of strongly interacting matter emerge from fundamental interactions Lattice QCD predicts a rapid transition, with correlated deconfinement and chiral restauration In a nutshell
• Study Matter under Extreme Conditions of temperature (100,000 times that of the center of the Sun) and density • ‘state of matter’ at high temperature & energy density: TheThe QGPQGP – ground state of QCD & primordial matter of the Universe • partons are deconfined (not bound into composite particles) • chiral symmetry is restored (partons are ~ massless) – ‘the stuff at high T where ordinary hadrons are no longer the relevant d.o.f’
• Mission of Ultrarelativistic Heavy Ions – search for the QGP phase – measure its properties – discover new aspects of QCD in the strongly coupled regime • Answer some of the most fundamental questions about our Universe and its development – A small “big bang” in the laboratory…. What do we measure? Language • We all have in common basic nuclear properties – A, Z … • But some are specific to heavy ion physics
–v2 Fourier coefficient of azimuthal anisotropies “flow” 1 if yield = perturbative value from initial parton-parton flux –RAA –T Temperature (MeV)
– μB Baryon chemical potential (MeV) ~ net baryon density 3 – η Viscosity ( MeV ) indirectly inferred from RAA and v2 –s Entropy density ~ “particle” density
dE T 1 dE T – ε Energy density (Bjorken 1983): ε = = 2 A T dz πR τ dy Collision Geometry In these complicated events, we have (a posteriori ) control over the event geometry: Centrality → impact parameter (b) spectators selection on collision geometry z
“peripheral” => b ~ bmax “central” => b ~ 0
For a given b, Glauber model participants: gives Npart nucleons in y and Nbin coll nuclear overlap x spectators 1234 Measured with Zero Degree Calorimeters Detecting the spectator nucleons ZP ~ 100m away from theinteraction point Or via transverse energy / part. multiplicity ZN Space-time Evolution of the Collisions p time γ e φ jet K π μ Λ γ e Freeze-out (~ 10 fm/c) (no more elastic → collisions)
n o Hadronization si n particle composition pa is fixed (no more x E inel. Collisions) → QGP (~ few fm/c)
Hard Scattering + Thermalization space (< 1 fm/c)
Pb Pb @2000: 25 countries, HI experiments at the SPS about 500 physicists involved strangeness, hadron spectra, large acceptance Ongoing!
2009 NA61 (SHINE) muons
multistrange electrons NA60 2000 strangeness, NA49 NA57 exotics hadron spectra photons Pb NA50 NA52 WA97 NA45 WA98 1994 (Ceres) NA44 muons NA34/3 WA94 (Helios-3) strangeness S NA35 NA36 WA85 NA34(Helios-2) NA38 WA80 1986 HADRONS LEPTONS, PHOTONS Experiments at RHIC STAR Both running (energy scan) and being upgraded PHENIX • Hadronic Observables • Leptons, Photons, & Hadrons • Large Acceptance (TOF, HBD, Vertex dets)
BRAHMS PHOBOS 95° Inclusive Particle Production, Charged Hadrons, Large Rapidity Range Particle Correlations 30° 2.3°
Both completed 30° 15° A few fundamental results • Experimental results have been populating the phase diagram • The fireball emits hadrons fron an equilibrium state – All data at the different energies are in agreement with a thermal model with 3 parameters: T, μB , V – A limiting temperature emerges as a function of c.m. energy , matching predictions from Lattice QCD for a phase limit • The fireball expands collectively like an almost ideal fluid – hydrodynamic flow characterized by azimuthal anisotropy coeffient v2 – The system has very low viscosity (close to the AdS/CFT limit) – Flow builds up at the partonic level • At high T (RHIC energies) the matter produced is opaque to hard probes (high-pT particles suppressed, opposite-side jet absorbed) • At RHIC multiplicities consistent with gluon saturation effects
What is going on?
– The field, which is largely data-driven, has seen a major development in the last few years, both in theory and experiment, and has ambitious plans for the coming decade: • A vigorous exploration of the QCD phase diagram
– In the high-μB direction – In the high-T direction – At the liquid-gas boundary • Different methods and approaches, with a common aim: a qualitative step towards a description of high-density and temperature nuclear matter calculable from first principles Exploring high baryon densities
A field of great interest! Search for the CB M critical point, study phase transition, EOS
• CERN: – NA61 (SHINE) experiment • RHIC – Energy scan • GSI: – A very lively program ongoing at SIS (FOPI, KaoS, HADES) – A rich future: FAIR (CBM) MPD • 100*SPS beam intensity • DUBNA – NICA HI collider with MPD Detector: • Good systematics (like RHIC) • High rate (10* SPS)
Second Generation Experiments Critical point, critical phenomena Critical Opalescence as observed in
CO2 liquid-gas transition
T. Andrews. Phil. Trans. Royal Soc., 159:575, 1869
T > TC T~TC T < TC Current : SPS - SHINE A significant difference between freeze-out and transition temperature can lead to dilution of the signatures of the QCD critical point. One way address this is to vary system size/colliding ion size.
F. Becattini et al., PRC 73, 044905 What is the difference vs. NA49 ? Experimental set up : New spectator calorimeter for centrality selection Forward Time-Of-Flight Beam pipe TPC readout speed Physics Program : Studying QCD Critical Point and Onset of various observations with varying colliding ion size, collision centrality and having a proper p+p baseline RHIC Critical Point Search Program Hadron Mass
200 GeV
62.4 GeV Beam Energy
9.2 GeV
Uniform acceptance for different particle species and for different beam energies in the same experimental setup (advantage over fixed traget expt.) PROBLEM: low luminosity at low energy Future: CBM @ FAIR CBM at SIS 300 will start in > 2017 Claudia Hoehne 10-45A GeV beam energy, high availability of beam (order of 10 weeks per year), interaction rates up to 10 MHz “CBM light” at SIS 100 in 2015 Au beam up to 11A GeV, p beam up to 30 GeV (multistrange hyperons, charm production in pA)
Assume 10 weeks beam time, 25A Gev Au+Au (minbias), no trigger, 25 kHz interaction (and storage) rate: • “unlimited statistics” of bulk observables, e.g. ~1010-11 kaons, 1010 Λ CBM physics program: • low-mass di-electrons with high statistics, Equation-of-state 6 10 ρ, ω, φ -mesons (each) at high ρB (3-10 ρ0) • multistrange hyperons with high statistics, Deconfinement phase transition 108 Ξ, 106 Ω QCD critical endpoint Chiral symmetry restoration
High luminosity, rare probes, higher μB reach Phase diagram exploration • Lattice and other QCD based models :
– μB = 0 - Cross-over
–TC ~ 170-195 MeV
– μB > 160 MeV - QCD critical point • No signatures of QCD critical point established, possible hints at SPS
NICA strategy: Collider advantages with high rate => complementary program NICA @ max baryonic densities
NICA √s = 9AGeV The High-Energy Frontier: LHC as an Ion Collider • Running conditions for ‘typical’ Ion year:
Collision √sNN L0
PbPb 5.5 1027 70-50 106 * * 7.7
** ∫ L dt ~ 0.5 nb-1/year A x28 jump in energy as compared to RHIC • Running plan: – First short low-luminosity run (~1/20th design, i.e. L ~5x1025 cm-2s-1) • late 2010 (confirmed) – Following few years (1HI ‘year’ = 106 effective s, ~like at SPS) • 2 - 3 years Pb-Pb : targeting integrated L ~1nb-1 L ~ 1027 cm-2s-1 • 1 year p - Pb ‘like’ (p, d or α ) L ~ 1029 cm-2s-1 • 1 year light ions (eg Ar-Ar) L ~ few 1027 to 1029 cm-2s-1 – Later: different options depending on Physics results LHC vs RHIC • Unexplored low x regime. • Energy density and QGP lifetime increase by a factor 2 ÷3
• But also new probes: Jets, Heavy Quarks HI Experiments at the LHC • One dedicated Heavy-Ion experiment: ALICE – Needs to cover essentially all relevant observables – Designed to be able to cope with the highest multiplicities – The design evolved with time (latest addition: EMCAL) – Now over 1000 Physicists from 100 Institutions in 30 Countries • CMS and, to a lesser extent, ATLAS progressively expanded their interest in the Heavy-Ion runs – Very healthy competition! – Now about 150 Physicists involved – Major role or Russia (especially in CMS, O. Kodolova leads the HI Physics Group) ALICE is different… • What makes ALICE different from ATLAS, CMS and LHCb ? – Experiment designed for Heavy Ion collision • only dedicated experiment at LHC, must be comprehensive and be able to cover all relevant observables • VERY robust tracking – high-granularity detectors with many space points per track, very low material budget and moderate magnetic field
• PID over a very large pT range • Hadrons, leptons and photons
• Very low pT cutoff • Excellent vertexing • Complementary to the other experiments Experimental Constraints from the Heavy Ion running
– extreme particle density (dNch/dη ~ 2000 – 8000) • x 500 compared to pp @ LHC
– large dynamic range in pT: • from very soft (0.1 GeV/c) to fairly hard (100 GeV/c) – lepton ID, hadron ID, photon detection – secondary vertices – modest Luminosity and interaction rates • 10 kHZ (Pb-Pb) to 300 kHZ (pp) (< 1/1000 of pp@1034) Tracking challenge
Excellent tracking + vertexing + PID capabilities are the key factors
With part of the event removed, displaced vertices can be seen Ξ− →Λπ − ALICE Experimental Solutions
• dNch/dη: high granularity, 3D detectors (560 million pixels in the TPC alone, giving 180 space points/track, largest ever: 88m3), large distance to vertex (use a VERY large magnet )
– emcal: high-density crystals of PbWO4 at 4.6 m (typical is 1-2 m !)
• pt coverage: thin det, moderate field (low pt), large lever arm + resolution (large pt) 2 –ALICE: < 10%X0 in r < 2.5 m (typical is 50-100%X0), B= 0.5T, BL ~ like CMS ! • PID: use of essentially all known technologies – dE/dx, Cherenkov & transition rad., TOF, calorimeters, muon filter, topological • rate: allows slow detectors (TPC, SDD), moderate radiation hardness The ALICE detector
Size: 16 x 26 meters Weight: 10,000 tons ALICE Design Performance
TPC acceptance = 90%
Low material budget Ælow pt cut off Momentum resolution ~ 5% @ 100 GeV/c
PID Impact parameter resolution < 60 μm (rφ) for pT > 1 GeV/c
+ decay topologies ((K0, K+, K-, Λ, φ, D) K and Λ beyond 10 GeV/c Who is ALICE Spain/Cuba ~ 1000 Members Romania Japan Brazil South Africa Korea from both NP and HEP USA Italy China communities India Croatia Armenia ~30 Countries Ukraine Mexico ~100 Institutes JINR Russia ~ 150 MCHF capital cost France (+ ‘free’ magnet) Netherlands Hungary History UK Greece Germany Sweden 1989-1996: Design Poland Finland Norway CERN Slovak Rep. Denmark 1992-2002: R&D Czech Rep. 2000-2010: Construction 2002-2007: Installation 2008 -> : Commissioning 3 TP addenda along the way: 1996 : muon spectrometer 1999 : TRD Russia and Italy are the 2006 : EMCAL largest national groups A decade of R&D…
In detector Hardware and VLSI Electronics In DAQ & Computing => successfully completed => in progress now across the decade of the 1990's: – scalable architectures with – Inner Tracking System (ITS) consumer electornics • Silicon Pixels (RD19) commercial components • Silicon Drift (INFN/SDI) (COTS) • Silicon Strips (double sided) • low mass, high density interconnects – high perf. storage media • low mass support/cooling – GRID computing –TRD • bi-dimensional (time-space) read-out, on-chip • trigger (TRAP chip) –TPC • gas mixtures (RD32) • advanced digital electronics • low mass field cage – EM calorimeter • new scint. crystals (RD18) –PID • Multigap RPC's (LAA) • solid photocathode RICH (RD26) ALICE in 2001 Insertion of final TOF super module Installation of final muon chamber
ALICE in 2008
Formal end of ALICE installation July 2008 2008: cosmics! Event Displays TRD TOF AC O and TP C Muon spectrometer SDD + SPD
TPC and TRD triggered by TRD41 2008: First Interaction in ALICE • LHC beam circulation tests on 11.09.2008. • Collision of beam-halo particle with SPD: 7 reconstructed tracks from common vertex. ALICE 2009: largely complete Complete: ALICE Status ITS, TPC, TOF, HMPID, FMD, T0, V0, ZDC, Muon arm, Acorde PMD , PHOS(3/5), DAQ
Partial: 2/3 HLT 7/18 TRD 4/12 EMCAL The First event! HowHow wellwell isis thethe detectordetector doing?doing?
HMPID TRD track Cherenkov Ring TPC track
TPC, TRD, TOF, HMPID On 6th December, ‘stable beams’ were declared & we could switch on all ALICE detectors for the first time..
ITS
Muon Spectrometer
45 17/12/2009 CERN J. Schukraft The first LHC Physics Paper!
Phase 1: rediscovering the standard model ( QCD in the case of ALICE) The average number of charged particles created perpendicular to the beam 009 v 2 No 28 in pp collisions at 900 GeV is: JC EP to ted mit dN/dη = 3.10 ± 0.13 (stat) ± 0.22 (syst) sub
last time measured at the ISR for pp
This is the first (and easiest) of many numbers we need to (re)measure to get confidence in our detectors, tune the simulations, study background, .... Discoveries are 4 still a long way to go.. Results are flocking in: by the way, National Geographic was sort of correct.. 0 K s →ππ Λ → πp
PDG: 1115.7 MeV PDG: 497.6 MeV
Just a few examples…
Λ → πp
PDG: 1115.7 MeV Φ → Κ+Κ− PDG: 1019.5 MeV Russian- JINR participation in ALICE Russia: 9 Institutions ¾ BINP (Novosibirsk) ¾ IHEP (Protvino) ¾ INR (Troitzk) ¾ ITEP (Moscow) ¾ MEPhI (Moscow) ¾ PNPI (Gatchina) ¾ RFNC “VNIIEF” (Sarov) ¾ RRC “Kurchatov Institute” (Moscow) ¾ St.PSU group (St. Petersburg) • JINR (Dubna) Everywhere in the project
¾ PHOS (KI, Sarov, IHEP, JINR) ¾ DIMUON (PNPI) 9 ¾ T0 (MEPhI, INR, KI) ¾ TOF (ITEP) 9 ¾ ITS (St.PSU) 9 ¾ Common Projects ⇒ survey, infrastructure ( A major one: the Muon Spectrometer Magnet Yoke at JINR) 9 ¾ Data analysis and physics (RRC KI, JINR, ITEP, IHEP, INR, St.PSU, PNPI, MEPhI, Sarov) 9 ¾ GRID computing infrastructure(RRC KI, JINR, ITEP, IHEP, INR, St.PSU, PNPI) 9 9 : In direct collaboration with Italian groups The muon magnet
Muon Filter
Field mapping device Muon Chambers: test and assembly at CERN Muon arm tracking chambers fabricated at PNPI
Slats during the pre-assembly tests
Slats fixed on the panel JWG, March 16, 2 007 … and more…
T0 installed TOF CRTF ITS Ladders
PHOS module # 2 Photon spectrometer PHOS Major Russian-led detector
5 independent modules each of 3584 crystal detector units PHOS cradle PHOS (PHOton Spectrometer) is a high resolution electromagnetic calorimeter consisting of 17920 detection channels based on lead-tungstate crystals(PWO). => Very far from Interaction Point to handle High Multiplicities
Kurchatov Institute, Sarov, IHEP(Protvino), JINR Oslo, Bergen, Prague, PHOS module crystal detector unit: Warsaw, Nantes, Muenster, Working temperature: PWO crystal+ APD+ Beijing, Wuhan, Hiroshima, -25 oC preamp. CERN Today:
• 3 modules PHOS installed and operational at nominal T of -20o from day 1 Y! AR IN IM • Even with the EL Y PR small statistics ER V π0 →γγ of the first 900 1 < p < 1.5 GeV GeV pp run… t first peak! What Physics in the First year?
• Ions in LHC in November 2010 – Tests with Pb all the way to LHC successful! • From now on pp ALICE detector performs very well in pp very low-momentum cutoff (<100 MeV/c) pp Physics -6 xT-regime down to 4×10 pt-reach up to 100 GeV/c excellent particle identification with ALICE efficient minimum-bias trigger Excellent vertexing capabilities start-up some collisions at 900 GeV → connect to existing systematics first physics in ALICE will be pp provides important reference data for pp first high energy run heavy-ion programme Ideal beam conditions for Minimum bias running ALICE at low luminosity unique pp physics in ALICE e.g. (50 ns scheme allows Physics at high multiplicities, reachable decoupling the luminosity thanks to the multiplicity trigger from the pixel detectors (7-10 times the mean in ALICE from the ones in muultiplicity of minimum bias collisions) ATLAS and CMS) Same set of measurements and themes of Heavy-Ion collisions (strangeness production, first year will typically give jet-quenching, flow, …) in ALICE Luminosity baryon transport 29 -2 -1 measurement of charm and beauty cross around 2·10 cm s sections down to very low transverse giving of the order of 109 momentum (major input to pp QCD physics) both open charm mesons and quarkonia events depending on run Essential the acceptance in the low- duration and efficiency transverse momentum region Ongoing!! HI Physics with ALICE, summary
fully commissioned detector & trigger early ion scheme alignment, calibration available from pp 1/20 of nominal luminosity first 105 events: global event properties ∫Ldt = 5·1025 cm-2 s-1 x 106 s multiplicity, rapidity density 0.05 nb-1 for PbPb at 5.5 TeV elliptic flow 8 NPbPb collisions = 4·10 collisions first 106 events: source characteristics 400 Hz minimum-bias rate particle spectra, resonances 20 Hz central (5%) differential flow analysis muon triggers: interferometry ~ 100% efficiency, < 1kHz first 107 events: high-p , heavy flavours t centrality triggers: jet quenching, heavy-flavour energy loss bandwidth limited charmonium production 7 NPbPbminb = 10 events (10Hz) 7 yield bulk properties of created medium NPbPbcentral = 10 events (10Hz) energy density, temperature, pressure heat capacity/entropy, viscosity, sound velocity, opacity susceptibilities, order of phase transition LHC, Physics of ‘The First 3 Minutes’: Multiplicity First estimate of energy density Saturation, CGC ? integrated multiplicity distributions from Au- Au/Pb-Pb collisions and scaled pp collisions
dNch/dy = 2600 saturation model Eskola hep-ph/050649
dNch/dy = 1200 ln(√s) extrapolation Before RHIC, predictions for the LHC were considerably higher, ranging up to
dNch/dy=8000 LHC, day 1 (105 events) : is the QGP an ideal fluid ?
LHC ?
• One of the first answers from LHC – Hydrodynamics: modest rise – Experimental trend & scaling predict large increase of flow ChemicalChemical compositioncomposition Particle composition can be described in terms of a statistical model (grand canonical ensemble) with 2 free parameters (thermalization temperature and bariochemical potential).
Consistent with a thermalization of the system with T ~ 170 MeV , μB ~ 30 MeV Limiting temperature reached for large sqrt(s). First data at LHC will check if the hypothesis survives at *20 the RHIC cm energy Parametrization of all freeze- out points • If the fit parameters are plotted vs. Sqrt(s), a limiting T emerges at about 160 MeV • First data at LHC will check if the hypothesis survives at *20 cm energy => “DAY 1 PHYSICS” 0 ALICE Pilot run Physics: ρ, φ,K* ,K s, Λ, Ξ, Ω…
Measure: 106 central Pb-Pb • strangeness production • medium modification of mass and widths Λ 7 10 events: Reconstruction rates: pt reach φ,K,Λ Λ: 13/event ~ 13-15 GeV Ξ: 0.1/event p reach Ξ,Ω Ω: 0.01/event t p : 1 to 3-6 GeV ~ 9-12 GeV T
ρ0(770) π+π− 106 central Pb-Pb
Mass resolution + - ~ 2-3 MeV φ (1020) K K
106 central Pb-Pb Hard Scattering as a Probe New for heavy ion physics → Hard Parton Scattering ~ impossible at SpS, interesting at RHIC, perfect at LHC •Jets leading particle → high pt leading particles hadrons → azimuthal correlations → jets in calorimeters
hadrons • Scattered partons propagate through matter leading particle radiate energy (~ few GeV/fm) in colored medium
• suppression of high pt particles called “parton energy loss” vacuum
or “jet quenching” medium • alter di-jets, azimuthal correlations, jet fragmentation function LHC vs RHIC hard probes
From RHIC to LHC
• Cross section for heavy flavours and jets grows by:
σcc → ~ 10 σbb → ~ 100 σjet>100GeV → ~ ∞
σRHIC(ϒ→ll) ~ σLHC (Z→ll)
N(qq) per central PbPb collision
SPS RHIC LHC charm 0.2 10 200 LHC is a Hard bottom - 0.05 6 Probes Machine! LHC: the realm of Jets Jet statistics in pilot Pb run Jets are produced copiously…
2 20 100 200 pt (GeV) 100/event 1/event 103 in first 106 Pb-Pb events
ALICE Acceptance 106 central PbPb collisions
410 106 8central central Pb-Pb PbPb eventscollisions (pilot (month) run) ET Njets threshold 4 1.56 10 105 3eventsevents 50 GeV 5 × 10 100 GeV 1.5 × 103 150 GeV 300 200 GeV 50 First full run Physics: D0 → K-π+ A major ALICE asset: measure Y, B, J/ψ and D in the same experiment: natural normalization, Bkgd subtraction, in central region identify J/ψ from B decays
• Golden channel for open charm •S/B ≈ 10% • Significance for 1 month Pb-Pb run (107 events) : S/√(S+B) ≈ 40
statistical.
systematic. The Future • After years of very successful collaboration between Italian and Russian & JINR Nuclear Physicists in ALICE, a very exciting future opens ahead of us: –ALICE Physics • ALICE will take data in its present form for at least 5-6 years (pp running + 1 year pilot PbPb, 2 years high Lum PbPb, 1 year pPb, 1-2 years of a lower-A nucleus). An extremely rich scientific program, which will see collaboration in analysis and computing. As early as possible PHOS should be completed. – ALICE upgrades • An extensive upgrade program is being studied, to extend the vertexing capabilities, Particle Identification at larger momenta, the overall rate capability and forward tracking and calorimetry (to access very low-x and therefore the physics of gluon saturation) – Experimentation at high baryon densities (MPD@NICA) • A new, challenging detector and a rich scientific program, opportunities of collaboration to be explored! spares SCIENCE Vol: 298 EllipticElliptic flowflow 2179 (2002) 7Li Elliptic flow coefficient
dn/dφ ~ 1 + 2 v2(pT) cos (2 φ) + ... Where azimuth is measured z y w.r.t. the reaction plane Flow: Correlation between coordinate x and momentum space => azimuthal asymmetry of interaction region trasported to the final state close particles move at similar velocity and direction flow builds up in an interacting medium with pressure gradient for given boundary conditions, flow 2v2 profile depends on Equation of State EoS and viscosity η of ‘fluid’ Hydrodynamics of perfect liquid: η = 0, λ = 0 (‘strongly interacting’) Ultra-cold 7Li Flow acts at early times 10-12 eV , 2 ms of expansion Flow “knows” quarks…
baryons
mesons
2 2 KET ≡ m + pT − m The fluid is strongly interacting => small viscosity
• Although the errors are large (especially from assumptions on initial spatial distribution: Glauber vs. CGC) the data rule out values of η/s much larger than 1/4π, the conjectured limit from AdS/CFT • Also measured from fluctuations, heavy quark motion,... • Most perfect liquid ever observed? One result among many: Photons shine, Pions (and η) don’t
• Pions are strongly absorbed in the Hot/dense medium, while direct photons are not